Collector electrodes are known for their use in storage cathode ray tubes for collecting secondary electrons that are emitted from written areas of a storage target by the action of flood or low velocity electrons being attracted to the positively charged written areas to allow bistable operation to take place.
Collector electrodes are part of the target structure in bistable storage targets to form an integral storage target as disclosed in U.S. Pat. Nos. 3,293,433; 3,293,474; 3,339,099; 3,401,293; 3,531,675; 3,956,662 and 3,978,366. The collector electrodes described in these patents are in various forms. One form is that of a conductive coating covering the inside surface of a faceplate with a porous storage dielectric layer disposed thereon so that secondary electrons are collected by the underlying collector electrode through the storage layer as taught by U.S. Pat. No. 3,293,433. Another form of collector electrode is a metallic mesh that is applied onto the inside surface of the faceplate and storage dielectric islands are provided in the mesh openings onto the faceplate surface which is covered in U.S. Pat. No. 3,293,474. The collector electrodes in U.S. Pat. Nos. 3,531,675; 3,956,662 and 3,978,366 cover metal-coated glass projections etched from an inside surface of the glass faceplate, metal particles forming an array of dots connected to a metal coating on the inside surface of the glass faceplate and metal-coated glass bead dots in the form of an array secured to the glass faceplate; these projections, dots and glass bead dots extending through a layer of phosphor dielectric storage material and beyond the top surface of the layer.
The above-described bistable storage targets will operate to display stored and nonstored information, but the displayed nonstored information is not very bright which makes it difficult to compare the nonstored information with stored information.
In order to increase the brightness of the nonstored information, it is known to add fluorescent phosphor material that does not store information to the storage dielectric material as disclosed in U.S. Pat. No. 3,339,099. The storage dielectric material in this patent however, is porous to enable the secondary electrons to be collected by the collector electrode on which the fluorescent phosphor material and storage dielectric material is disposed. This arrangement makes it difficult to process the storage dielectric material into a target layer and this requirement for a porous dielectric storage target limits light output and contrast ratio. In U.S. Pat. No. 3,401,293, the inside surface of the faceplate has cavities in which are located fluorescent phosphor material. A metal coating covers the fluorescent material and storage dielectric material is provided as dots onto the top surface areas of the faceplate adjacent the metal-coated fluorescent material with the metal coating defining the collector electrode. The metal coating of the fluorescent phosphor material acts as a collector and increases the brightness of the nonstored information, but the addition of the metal coating is expensive.